fix(sso): send the PKCE verifier for GitHub login (#1534)

plugins/sso/src/backend/login.ts

@@ -194,7 +194,6 @@ export function createSsoLogin(ctx: PluginContext, store: ProviderStore) {
     config: OidcConfig,
     code: string,
     pending: PendingState,
-    withVerifier: boolean,
   ): Promise<Record<string, unknown>> {
     const response = await fetch(config.token_url, {
       method: "POST",
@@ -208,7 +207,7 @@ export function createSsoLogin(ctx: PluginContext, store: ProviderStore) {
         client_secret: config.client_secret,
         code,
         redirect_uri: pending.backendCallback,
-        ...(withVerifier ? { code_verifier: pending.codeVerifier } : {}),
+        code_verifier: pending.codeVerifier,
       }),
       ...buildFetchOptions(config.ca_cert),
     } as RequestInit);
@@ -231,7 +230,7 @@ export function createSsoLogin(ctx: PluginContext, store: ProviderStore) {
     code: string,
     pending: PendingState,
   ): Promise<PluginVerifiedIdentity> {
-    const tokenData = await exchangeCode(provider.config, code, pending, false);
+    const tokenData = await exchangeCode(provider.config, code, pending);
     const fetchOptions = buildFetchOptions(provider.config.ca_cert);
     const headers = {
       Authorization: `Bearer ${tokenData.access_token}`,
@@ -341,7 +340,7 @@ export function createSsoLogin(ctx: PluginContext, store: ProviderStore) {
     pending: PendingState,
   ): Promise<PluginVerifiedIdentity> {
     const { config } = provider;
-    const tokenData = await exchangeCode(config, code, pending, true);
+    const tokenData = await exchangeCode(config, code, pending);
 
     let userInfo: Record<string, unknown> | null = null;
     const claimSources: Record<string, unknown>[] = [];

plugins/sso/tests/backend/sso.test.ts

@@ -1,3 +1,4 @@
+import { createHash } from "node:crypto";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import {
   LEGACY_DDL,
@@ -356,6 +357,19 @@ describe("the callback", () => {
       "GET",
       `/callback?code=abc&state=${url.searchParams.get("state")}`,
     );
+    const exchange = vi
+      .mocked(fetch)
+      .mock.calls.find(
+        ([url]) =>
+          String(url) === "https://github.com/login/oauth/access_token",
+      );
+    const token = new URLSearchParams(String(exchange?.[1]?.body));
+    const verifier = token.get("code_verifier");
+    expect(verifier).toBeTruthy();
+    expect(url.searchParams.get("code_challenge_method")).toBe("S256");
+    expect(createHash("sha256").update(verifier!).digest("base64url")).toBe(
+      url.searchParams.get("code_challenge"),
+    );
     expect(callback.body.identity).toMatchObject({
       provider: String(created.body.id),
       subject: "42",